Reference List: Expression and Development of Maximal Muscle Power

Innervations
home about us contents products downloads support education
contact info request info what's new search currency converter

Osteoporosis: Investing in your bone bank

Robert U. Newton Ph.D. and Brendan Humphries Ph.D.

It has been estimated that by the year 2010 osteoporosis alone will cost the Australian health care system over one billion dollars per annum

Osteoporosis is one of the most prominent bone conditions in the world and is characterised by a decreased mass per unit volume of bone mineral content accompanied by deterioration in the quality of the micro-architectural structures, compromising skeletal integrity and resulting in a decreased resistance to fracture. Although commonly associated with menopausal women, osteoporosis is also becoming a significant problem for aging men.

In women, the rapid decline in oestrogen associated with aging culminates with the commencement of menopause and is evidenced by accelerated losses of bone mineral density (BMD). Hormone replacement therapy has been advocated to arrest the rapid loss of BMD associated with menopause. However, it has been suggested that in the absence of weight bearing activity no amount of endocrine intervention can or will maintain BMD. Similarly, the majority of the research reports that calcium supplementation is not effective for maintaining BMD although its efficacy may be demonstrated if undertaken in conjunction with appropriate exercise. What is clear is the importance of regular physical activity, weight bearing, and of sufficient intensity to maintain bone health.

The combination of muscular contractions and gravity are the two primary mechanical forces that effectively initiate bone responses. Evidence from the literature suggests that high levels of muscular strength provide a localised stimulus to the skeletal sites of muscle attachment thus providing a positive influence on bone mass. In contrast, a loss of skeletal mass and integrity is exemplified in conditions of reduced loading, such as bed rest, space flight and decreased muscular activity.

There have been a large number of studies examining exercise training programs to attenuate the parallel decline in muscular strength and bone mass with advancing age. Exercises that introduce high strain levels to the skeleton are typically not performed with increasing age yet have been proven to be effective in increasing both BMD and strength levels. Activities that incorporate low to moderate intensity exercise have returned mixed results in elderly adults with relatively small gains in strength and inconsistent changes to bone. Prior to the industrial age, the human was required to lift and carry considerable weights whether it be toting water and food, working in the fields or constructing shelters. Such activities were effective for maintaining bone mass yet today the majority of us never perform any heavy lifting or carrying. Exercises that are common to daily living e.g. walking, have been the least effective in bone mineral accretion. The stress placed on the bone during such low intensity activity is simply insufficient to stimulate remodelling and increases in BMD. Some practitioners have recommended swimming and other water-based exercise as effective for maintaining bone health. Although there are considerable positive aspects to such exercise methods, because they are not land-based, weight bearing and of sufficient intensity, such exercises should not be prescribed for maintenance or rehabilitation of BMD. Heavy resistance training has been shown to have the most potent effect on bone growth.

Recommendations for a Bone Health Exercise Program

Before commencing any exercise program it is advisable to have a medical examination to ensure that the person does not have any conditions which might preclude them from participation. This is particularly true for anyone over 35 years of age and/or who has increased risk of having cardiovascular disease e.g. high blood pressure, smoker, family history of cardiovascular disease etc. Also, if the person has been diagnosed with osteoporosis then close monitoring and evaluation is required as the bones are already weakened and may not be able to withstand the exercise stress.

The goal of the exercise program is to increase muscle strength while placing stress on the bones. Due to the debilitating effects of osteoporosis on the spine and femur (thigh bone) the exercises have been chosen to specifically target these areas. This exercise program is not a complete lifestyle exercise program in itself but should be combined with other physical activity such as walking, swimming, cycling as well as a more complete resistance training program. Stretching to maintain flexibility should also be prescribed.

Squat

Strengthens the quadriceps, gluteals, lower back, hamstrings and calf muscles while placing stress on both the vertebral column and hip region. Initially squats may be performed without any additional load other than body weight, however as strength increases resistance can be added by holding weights in the hands or supported across the shoulders.

Dead lift

A more advanced lift and difficult to perform correctly. This should only be prescribed after monitored instruction. The dead lift is an excellent exercise for training the muscles of the upper and lower back, gluteals and hamstrings. The exercise applies forces through the spine and femurs and so theoretically should stimulate bone development. Again, additional weight can be added as the person’s strength progresses.

Sit-ups

Apart from strengthening the abdominal muscles, which is important for posture and supporting the trunk, sit-ups also place force through the spine.

Back extensions

Strengthens the muscles that extend the spine and so help to stabilise and support the trunk. Also exerts forces through the spine.

Volume and Frequency

Each set of exercises should consist of 8-12 repetitions. When initiating the program only one set of each exercise, one session per week should be completed for the first two weeks. This should be increased to 2 sets in the third week and then 4 sets in the fourth week. From then on 3 sets of each exercise can be completed in each session. The optimal volume and frequency of resistance exercise for increasing strength is not known at this time and even less is understood about the exercise parameters necessary to increase or maintain bone mass. It is prudent however to assume that 1-2 sessions per week are necessary. As the exercises involve large muscle groups that require several days for recovery from exercise, completing more than 2 sessions per week is not warranted. However, splitting the routine and performing the squat exercise or dead lift at alternate sessions may allow an increase to 3 or even 4 workouts per week. The efficacy of this in terms of bone mass accrual is not known at this time however.

Complete either the squat or dead-lift exercises first and then finish with the back extensions and sit-ups. It is important not to fatigue the trunk stabiliser muscles before the heavy compound lifts.

Cross sectional studies have shown that prior occupation and physical activity level have a profound effect on BMD throughout life. By building up the amount of bone tissue, it is far less likely that as a person ages his or her BMD will fall to the level which is critical for fracture. The take home message here is to build up the bone mass during adolescence and early adulthood and this will have a considerable preventive effect. Regular exercise and in particular resistance training throughout life is an important investment in your “bone bank”.